In some cases, a mark such as an alignment mark to be used for positioning in processing a substrate such as a glass substrate is desired to be formed in a resin layer which is composed of a resin sheet attached on each of front and back surfaces of the substrate. Meanwhile, as a method of forming an alignment mark on a substrate, a method performed by machining means such as a drill disclosed in Japanese Patent Application Laid-Open Publication No. 2007-7776 (Patent Document 1) has been conventionally known. When the alignment mark is formed in the resin layer of the substrate according to this method, a crack is caused in the glass substrate at the position where the alignment mark is formed.